Can someone help me decode this sig part number?

[rvp82]

I was looking at a P220 compact and the seller told me the part number is as follows:

220BRC3BSSSAO

Here is what I have found so far:

220 - for P220
B - Beavertail
R - Rail (?)
C3 - ?
B - Black
SS - night sights
SAO - Single Action only.

Can you guys point out if Im wrong or help me figure out what the C3 is? Also, shouldnt there be a 45 in there? Thanks for the help!!

Here is the description:

Sig Sauer Custom 220 Limited Edition compact pistol, chambered in 45 ACP, single action only, blue durable Nitron matte finish, elite beavertail frame, aluminum factory grips, SigLite night sights, ambidextrous safety,

[aca72]

http://classic.gunauction.com/search/displayitem.cfm?itemnum=10863831

[rvp82]

I saw that picture but I was thinking that the "R" was for a rail and was hoping to figure out what the C3 meant.

[NikePenguin]

My guess is C3 is for the aluminum grips.